1. Field of the Invention
The present invention relates generally to semiconductor substrate processing equipment, and more particularly to providing a localized ultra-clean mini-environment for substrate processing.
2. Description of the Related Art
In the manufacture of semiconductor devices, processing equipment is highly automated in order to speed transfer between processing steps. To effect the automation, there exists a large amount of moving mechanical equipment such as robots and automated doors. Any moving mechanical equipment may be a particle generator. The generated particles can be deposited on a substrate in the proximate area of the moving equipment. In addition, the particles may become entrained in air patterns within the processing module, thereby becoming capable of being deposited on any wafers or substrates within the processing module. The generated particles can cause substantial damage to semiconductor circuits formed on the wafer. For example, the particles deposited on the wafer may be entrapped by a thin film deposited on the wafer in the next processing step and render the circuit useless through this latent defect.
Semiconductor processing equipment typically employs the use of slot valves for the transport of wafers between modules. The valve covers a slot, port, aperture, etc. that is provided in the wall of the interfaced chambers, thereby isolating the chambers when the door is in a closed position. When a wafer is being transferred between modules the door will open to allow for passage of the wafer. The valves have moving mechanical parts and compressible o-rings capable of generating particles. Additionally, the valves also have an added disadvantage in that they can be located in a static air flow environment of the storage facility or processing module. In such a case, particle density in static slow moving or recirculating air surrounding a particle generation source can quickly rise. Semiconductor devices on wafers exposed to such contamination levels are at risk to damage due to particle deposition.
FIG. 1A depicts a typical semiconductor process cluster architecture 100 illustrating the various chambers of the architecture. Vacuum transport module 106 is shown coupled to three processing modules 108a-108c which may be individually optimized to perform various fabrication processes. By way of example, processing modules 108a-108c may be implemented to perform transformer coupled plasma (TCP) substrate etching, layer depositions, and/or sputtering. Connected to vacuum transport module 106 is a load lock 104 that may be implemented to introduce substrates into vacuum transport module 106. The load lock 104 is coupled to an atmospheric transport module (ATM) 103 that interfaces with the clean room 102. The ATM 103 typically has a region for holding cassettes of wafers and a robot that retrieves the wafers from the cassettes and moves them into and out of the load lock 104. As is well known, the load lock 104 serves as a pressure-varying interface between vacuum transport module 106 and the ATM 103. Therefore, vacuum transport module 106 may be kept at a constant pressure (e.g., vacuum), while the ATM 103 and clean room 102 are kept at atmospheric pressure.
FIG. 1B illustrates a partial system diagram 110 including an atmospheric transport module (ATM) 111 which includes a filter/blower 112. The filter/blower 112 is configured to generate an air flow 114 in the ATM 111. In addition, the ATM 111 is shown connected to the load lock 116. Although this type of prior art ATM 111 is capable of transferring wafers 124 from the cassette 126 into and out of the load lock 116 quite efficiently, the air flow 114 has been intended to flush particles away from the area in close proximity to the slot valve 118. However, mechanical or other design constraints may preclude achieving an optimum air flow in certain important regions of ATM 111. As a result, the air flow pattern is not the downward sweeping action 114, but rather more of a circular flow 124 or even a substantially static environment. Load lock 116 is isolated from ATM 111 by slot valve 118 making a seal 120. For example, the seal 120 may be an o-ring type seal. The wafer path 122 proceeds through the area defined by the non-sweeping air flow pattern.
During the opening and closing of the slot valve 118 when the door opens and shuts against the seal 120, particle bursts are generated through the contact of the seal and the door or other mechanically contacting surfaces. It can be appreciated that there is some pressure exerted against the seal by the slot valve in order to isolate the chambers on either side of the closed slot valve. In addition, particles trapped between the seal and the door may be released as the door opens. Therefore, the generated particles become entrained in the air flow patterns in the vicinity of the slot valve and can deposit themselves onto wafers traveling through or near the slot valve opening.
Any particles that have been deposited onto the surface of the wafer may remain on the wafer through its processing stage. These particles may cause defects in semiconductor circuits fabricated thereon, resulting in extra costs and lower yields. In some cases, the particles can migrate through an open slot valve door resulting in the potential contamination of both chambers. This problem is not limited to ATM 111 environments, but can also occur at any location where moving parts are in proximity to wafers or wafer transport paths, where off-gassing occurs and where the airflow is non-optimum. It can be appreciated that the processing equipment used in semiconductor manufacturing may include numerous moving mechanical parts capable of generating particle bursts. While the particle bursts may not be completely eliminated, the particles must be removed from the substrate path prior to the substrate moving through the vicinity of the particle burst so that the particles are not deposited on the substrate.
In view of the foregoing, what is needed is localized air flow augmentation to sweep any generated particles away from the substrate path and out of the processing module to eliminate particles from being deposited on substrates.
Broadly speaking, the present invention fills these needs by enhancing an ultra-clean mini-environment with localized air flow augmentation. The mini-environment is preferably configured to generate the air flow in a proximity region around a particle generating device. It should be appreciated that the present invention can be implemented in numerous ways, including as an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a transport passage for transport of a wafer between a first chamber and a second chamber is disclosed. The transport passage includes an air flow supply for directing air flow from a top region towards a bottom region of the first chamber. A moveable door for opening and closing an aperture is also included. The aperture is defined on a wall between the first chamber and second chamber and located between the top region and the bottom region of the first chamber. The aperture further defines a passage between the first chamber and the second chamber. A cowl defining an enclosure in a proximity region of the moveable door is also included. The cowl has a top portion that is more proximate to the top region of the first chamber and a bottom portion that is more proximate to the bottom region of the first chamber. A fan is disposed in proximity to the bottom portion of the cowl so as to augment air flow from around the proximity region at the moveable door and through the enclosure defined by the cowl.
In another embodiment, an air flow enhancer for creating a reduced particle mini-environment in a vicinity of a wafer presence is disclosed. The air flow enhancer has an air flow supply for directing air flow from a first region toward a second region. A cowl defining an enclosure in a proximity region of the particle generating device and having a top portion and a bottom portion is included. The cowl being situated so that the top portion is more proximate to the particle generating device. A fan is disposed in proximity to the bottom portion of the cowl so as to augment air flow from around the proximity region and through the enclosure defined by the cowl.
In yet another embodiment, a method for creating a reduced particle environment in a vicinity of a mechanically active transport passage interface between a first region and a second region is disclosed. The method includes generating an air flow in the first region, the air flow being directed from a first zone to a second zone of the first region. Then the active transport passage interface is transitioned. Next the air flow in the vicinity of the active transport passage interface is augmented. The augmentation further includes causing a sweeping air flow that is configured to remove particles in and around the vicinity of the active transport interface.
In still another embodiment, a method for enhancing an air flow for creating a reduced particle mini-environment in a vicinity of an active particle generating device is disclosed. The method includes generating an air flow directed from a first region towards a second region. Then the air flow in the vicinity of the active particle generating device is augmented. The augmentation further includes creating a sweeping air flow to remove particles in and around the vicinity of the active particle generating device.
The advantages of the present invention are numerous. Most notably, the augmented air, flow creates a flushing action which entrains particles in the mini-environment, thereby removing the particles from the proximity region of the transport passage interface or the particle generating device. In addition, the augmented air flow eliminates static air flow regions from which the particles can be deposited on the substrates or wafers. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.